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sur le développement des zones arides et semi-arides

Titre : Alleviation of drought stress on Vigna radiata L. by using glycinebetaine, proline or their mixture

Auteur : Othman, Mohamed Othman Mohamed.

Etablissement de soutenance : Beni-Suef University

Grade : Doctor of Philosophy in Plant Physiology 2012

Résumé
The present investigation was conducted under the prevailing natural conditions in a fenced area in pots using clay loamy soil. In this experiment, mung bean (Vigna radiata L. var. Giza-1) seeds were treated by soaking, for 24 hours, in distilled water, 100 mM glycinebetaine (GB), 1mM proline (Prol) or their mixture (1:1), then each treatment was divided into two groups ; the first group was irrigated with tap water to adjust the soil water to field capacity (water content = 34.5 % oven dry soil = 100% FC) while second group was water stressed by adjusting the soil water content to reach 60% of the field capacity (60% FC). The obtained results showed that : 1- All investigated growth criteria [root length (R L), shoot length (Sh L), shoot fresh weight (Sh F Wt), shoot dry weight (Sh D Wt), shoot : root ratio (Sh/R)] and the investigated yield criteria [(pod no. /plant, pod length, seed no. /pod. seed no. /plant and weight of 100 seeds)] were retarded by drought stress, while application of GB, proline or their mixture alleviated the drought stress. On the other hand, all these investigated parameters were positively affected by treatments with GB, proline or their mixture when it was applied to plants irrigated with 100% FC. 2- Soluble carbohydrate fractions increased by drought stress while their was a reduction in the contents of the total carbohydrate fractions On the other hand, under non stress conditions, the application of GB, proline or their mixture alleviated the stress symptoms and increased the contents of the carbohydrate fractions. 3- In the investigated mung bean plants, water stress resulted in an increase of the total amino acids (especially proline) and GB and reductions in the contents of protein and total nitrogenous fractions.The screening of individual amino acids showed no rational disturbance between them except proline. On the other hand, application of GB, proline or their mixture alleviated these stress symptoms and enhanced these fractions when applied under 100% FC. 4- Both of total fatty acids and lipids were reduced in water stressed plants while the application of GB, proline or their mixture alleviated these stress symptoms and enhanced these fractions in non stressed ones. 5- Photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) and photosynthetic efficiency were significantly decreased and retarded by drought application while application of GB, proline or their mixture alleviated these stress symptoms and enhanced these fractions in non stressed plants. 6- All investigated antioxidant enzymes [Superoxide dismutase (SOD), Catalase (CAT), Ascorbate peroxidase (APX), Peroxidase (POD), Glutathione reductase (GR) and Monodehydroascorbate reductase (MDAR)] showed high activities due to drought stress while all investigated hydrolyzing enzymes [α- amylase, β-amylase, protease and lipase] were inhibited. Application of GB, proline or their mixture alleviated these stress symptoms and enhanced these enzymes in non stressed plants. 7- Water stress resulted in the reduction of the contents of nutrient elements ; N, K, P, Cu and Fe and their total content, while application of GB, proline or their mixture alleviated these stress symptoms and enhanced these fractions when applied to non stressed plants.

Présentation étendue (EULC)